Impact of COVID-19 second booster vaccine on all-cause death among older cohorts

In a recent article posted to the Preprints with The Lancet* server, scientists illustrated that the second booster dose of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination lowered all-cause death in long-term care home residents and those aged 80 years or older.

Background

The emergence of the SARS-CoV-2 Omicron (B.1.1.529) variant radically altered the course of the coronavirus disease 2019 (COVID-19) pandemic, resulting in a tide of new cases, particularly among the frailest and oldest residents in long-term care facilities (LTCFs). Since these individuals are at an increased risk of severe COVID-19 consequences, their protection is of public health significance. Nine European nations, including Sweden, have recommended a second booster dose of the SARS-CoV-2 vaccination for certain susceptible groups, such as LTCF residents, by April 5, 2022. 

Data on the immunity provided by the second booster in this cohort is critically needed to minimize premature mortalities and guide vaccination plans and initiatives. In addition, details on all-cause deaths could impart deep insights into undocumented SARS-CoV-2-related deaths. However, the influence of a second SARS-CoV-2 vaccine booster dose on the frail and elderly and their impact on all-cause mortality risk in these cohorts remains unclear.

About the study

In the present registry-based, nationwide, matched cohort, retrospective study, the scientists examined the comparative vaccine efficacy of a second COVID-19 vaccine booster dose towards all-cause death in the ≥80 years aged people and long-term care facilities (LTCF) residents during the SARS-CoV-2 Omicron predominant phase in Sweden.

The team established two countrywide matched groups utilizing Swedish nationwide records. In the initial cohort, 25,252 LTCF residents who were immunized with a second booster dose of either COVID-19 messenger ribonucleic acid (mRNA)-1273 or BNT162b2 vaccines from January 1, 2022, onwards were paired 1:1 on the county of residence and birth year to inhabitants who only received the first booster shot. The second cohort comprised all people aged 80 or older in Sweden who received the second booster and was paired 1:1 with individuals who received the first booster, yielding 397,394 participants. The vaccination date in second booster recipients served as the baseline for each matched pair. The researchers monitored for all-cause death up to March 29, 2022, among these participants.

Findings and discussions

Overall, the study results depicted that relative to the first COVID-19 booster vaccine shot, the second booster dose of either SARS-CoV-2 mRNA-1273 or BNT162b2 vaccines reduced the transient risk of all-cause death among LTCF residents by roughly one-third during the Omicron dominant timeframe. Furthermore, a second booster dose minimized the risk of mortality among the elderly living at home by 50%. As a result, promoting a high uptake of COVID-19 booster vaccine shots was critical for preventing early fatalities.

The authors found that over a median follow-up of three weeks, there were 330 fatalities in the LTCF sample starting one week after baseline. Subjects who received a second booster shot had a mortality rate of 58.9 per 100,000 person-days relative to 71 for first-booster recipients in this cohort. The second booster dose of the COVID-19 vaccine demonstrated a 31% adjusted relative vaccine efficacy compared to the first shot. 

Additionally, there were 1025 fatalities in the cohort of all people aged ≥80 years in an average follow-up of 20 days. Moreover, among these subjects, people vaccinated with a second booster dose exhibited a mortality rate of 11.3 per 100,000 person-days, whereas it was 15·5 for the first-booster recipients. In this group, the adjusted comparative vaccine efficacy of the COVID-19 second booster dose was 42%, with improved efficiency when contrasted to first-booster recipients who had been vaccinated for more than four months. Notably, the benefits were higher for those living in their own homes and males relative to females.

Conclusions

The study findings demonstrated that relative to a first booster dose of SARS-CoV-2 vaccination, a second booster dose of either mRNA-1273 or BNT162b2 vaccines was linked to a lower risk of mortality from all causes in LTCF inhabitants and the elderly during the Omicron predominant period at least transiently. The present findings corroborate the advantages of the second booster on severe complications of COVID-19 in this cohort using a less biased and robust all-cause mortality outcome.

Overall, the current study showed that encouraging frail and older people to take booster doses of COVID-19 vaccines might prevent premature mortalities. The team suggested that more investigations are required to determine the longevity of the protection imparted by the second SARS-CoV-2 booster vaccine shot.

*Important notice

Preprints with The Lancet publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Shanet Susan Alex

Shanet Susan Alex, a medical writer, based in Kerala, India, is a Doctor of Pharmacy graduate from Kerala University of Health Sciences. Her academic background is in clinical pharmacy and research, and she is passionate about medical writing. Shanet has published papers in the International Journal of Medical Science and Current Research (IJMSCR), the International Journal of Pharmacy (IJP), and the International Journal of Medical Science and Applied Research (IJMSAR). Apart from work, she enjoys listening to music and watching movies.